Today I went to use my 4x4 , I turned the switch on the dash and nothing happened, no light on the dash and I didn't hear it engage. I tried high and low, both didn't work. This is the first time it has done this.

I was driving at about 5 mph for about a half an hour before I went to use it. I was off road. I kept trying it and still nothing. When I got back on road and up to normal speed I tired it again and it worked fine and has continued to work fine.

Any one have any idea why it could have not worked that time? Does the vehicle have to be at a certain speed for it to work? Could the slow speed I was traveling at for a long time cause the vacuum system not to have enough vacuum to engaged the 4x4?

 

Sounds like a vac leak, but if you have electric switch for 4x4 modes you need to stop and put it in neutral before selecting low, if it's above 3mph it won't select low, but this does not explain why you could not select hi... May need to do a vac test.

Regards,
Pete

 

Was it the first time you used 4x4 in quite a while? If so, you may have had what I can best decribe as a "lazy ESOF motor." If you don't use the system for long periods of time, the motor that actually shifts your transfer case tends to wake up from long naps kind of slowly - and sometimes not at all.

Check this thread out: https://www.f150online.com/forums/20...ore-snows.html

 

No, I used it a couple of days ago.

 

You can trouble shoot the vacuum system with this:

http://www.ford-trucks.com/forums/83...then-some.html

It's possible the solenoid is starting to fail.